The present invention is directed to a cleaning assembly for an agricultural combine, wherein the cleaning shoe is provided with a sieve having adjustable blades. The position of the blades is adjusted by an adjustment element that is coupled to a drive element located on the cleaning shoe. The sieve is removeably mounted to the cleaning shoe so that the sieve can be removed without disassembling the connection between the drive element and adjustment element.
In a combine some chaff and straw is mixed with the grain after threshing and separation. The cleaning assembly removes these contaminants from the grain. In most combines, the cleaning assembly contains three main components: a blower, an upper sieve and a lower sieve. The blower has its own housing, whereas the upper sieve and lower sieve are mounted on a cleaning shoe.
An adjustable sieve is designed from a series of transversely extending blades with rows of teeth. Each of these blades is fastened to a cranked shaft that has a crank arm engaged with an axially extending adjustment bar. All blades are moved simultaneously by axial displacement of the adjustment bar.
The adjustable upper sieve and lower sieve are adjusted as a function of the conditions of the harvested product. The blades of the upper sieve are opened or closed far enough so that the grain falls through the upper sieve before it travels the length of the upper sieve. If the upper sieve is opened too wide, the lower sieve can be overloaded with chaff. When the upper sieve is not opened wide enough and the grain cannot be separated from the chaff and straw, this reaches the upper sieve extension, which can lead to overloading of the return. If the grain cannot be separated there, either, as a result of a sieve being opened too widely, the grain is returned to the field over the end of the sieve as cleaning losses. The blades of the lower sieve must be opened wide enough to permit the grain to fall easily through them, but not wide enough that the straw and chaff can fall through.
In many combines, an operator, depending on the actual type of crop and the harvesting conditions, must reach between the side walls on the back side of the thresher in order to make these adjustments via hand levers mounted on the sieve. This makes the adjustments cumbersome and time-consuming. A common feature of hand-operated adjustment devices with linkages is that the operating elements are mounted in the cleaning shoe to avoid unnecessary deflection and therefore form a clogging hazard, that can adversely affect air conduction through the cleaning shoe.
Various remotely operated adjustment mechanisms have been proposed. U.S. Pat. No. 4,897,027 A discloses a cable drive mechanism that permits an operator to adjust the blade angle from an operator""s position. U.S. Pat. No. 5,586,033 A discloses an apparatus that drives the blades via a motor-driven cable mechanism for automatic control. A drawback of these sieve adjustments lies in the play of the operating devices, which leads to imprecise sieve adjustment. A relatively high disassembly expense is also required when the sieves, for example, must be disassembled for cleaning purposes.
A self-propelled combine is described in DE 198 24 462, in which the removable blade sieves are equipped with a spring that automatically brings the blades into the closed or open position. A lever rigidly mounted on the combine comes to bear on an adapter mounted with the adjustment bar of the blades when the sieves are incorporated in the cleaning shoe. The lever can therefore displace the adapter against the action of the spring in a first direction, in order to adjust the blades. If the lever is adjusted in the opposite direction, the adapter is pushed back by the action of the spring. This solution permits the sieve to be removed from the cleaning shoe without loosening a connection between the lever and the adapter. A shortcoming is that the sieves can no longer be closed or opened when they operate so sluggishly from contaminants or mechanical imprecision that the spring can no longer move the adjustment bars. It is also possible that the spring can fail because of barley glumes that are situated between the spring windings, so that the sieve can no longer be closed even when the blades are readily accessible.
It is an object of the present invention to provide an improved cleaning assembly having an easily removeable sieve with adjustable blades.
The invention refers to a cleaning assembly for a combine comprising a cleaning shoe having a removable sieve. The sieve has a frame with adjustable blades. The blades of the sieve can be moved by an adjustment element arranged on the sieve. The adjustment element is movable by a drive element that is mounted on the cleaning shoe. The drive element is not removable from the cleaning shoe with the sieve. The drive connection between the drive element and adjustment element is automatically disengaged when the sieve is disassembled and automatically reengaged when the sieve is reengaged. The drive element is set up so that it can drive the adjustment element in two directions. The adjustment element is therefore moved by the drive element in a first direction to open the blades and in the opposite direction, in order to close the blades. The drive element is therefore set up to actively drive the adjustment element in two opposite directions. A spring to return the adjustment elements is not required.
In this manner, the position of the blades is adjusted exclusively by the drive element, so that the spring is spared and the sieve remains adjustable even when the blades are difficult to access.
The drive connection between the drive element and the adjustment element can be any number of connections that readily disengage and engage. For example, the drive element may comprise a friction wheel that cooperates with a friction surface on the adjustment element. Such a friction drive system may encounter slippage in the drive element driving the adjustment element. A positive drive power transmission is preferred. For example, the drive element may comprise a gear that cooperates with a gear or rack on the adjustment element. The gear can be a standard spur gear or a worm gear. In the illustrated preferred embodiment, the adjustment element is provided with a rack, which is moved axially by the drive element that comprises a gear. The gear is mounted to the cleaning shoe. The described power transmission mechanisms automatically disengage on removal of the sieve from the cleaning shoe without additional assembly demands, and automatically reengages on incorporation of the sieve back into the cleaning shoe.
The sieves of the cleaning assembly are provided with a number of blades that normally extend transversely to the direction of travel of the combine. Each blade is generally equipped with a cranked shaft, which has a crank arm in order to adjust the angular position of the blade. The crank arms are accommodated in slots situated in an axially extending (i.e., along the forward direction of travel) adjustment bar. The angle of the blades and the opening produced between them is varied by movement of the adjustment bar forward or backward, produced by the adjustment element. However, it is also conceivable to rotate the adjustment bar and to convert the rotation to a displacement movement of the blade by appropriate mechanisms.
The drive element can be driven by an electrically, pneumatically or hydraulically powered motor, although a manual drive is also conceivable. The latter can be effected, in particular, from the operating cabin via appropriate power transmission elements. If the drive element is motorized, the motor can be controlled manually by appropriate switches in the operator""s cabin or by an automatic control or regulation device.
For reasons of flow, it is advisable to arrange as few elements as possible of the drive train of the drive element in the interior of the cleaning shoe. In a preferred variant, only the drive element and a shaft connected to it are therefore arranged in the cleaning shoe. The other elements of the drive train are then situated outside of the cleaning shoe.
The sieve is preferably fastened in the cleaning shoe by a retaining element. After removal of the retaining element, the sieve can be removed out the rear of the cleaning shoe.
Removal and insertion of the sieve can be effected by the drive element. After the retaining element has been removed, the drive element is placed in operation, which initially brings the blades into the closed or open position. If the blades are closed or opened, the adjustment element preferably cooperates with a stop so as not to unduly load the blades or even deform them. Since the retaining element was removed, the entire sieve is now removed from the cleaning shoe. Insertion of the sieve occurs in the opposite direction, also through the drive element.